Resistor value to colour code

Going the other way is the harder direction, because not every number can be painted on a resistor. Four bands hold two significant digits and five hold three, so 4.7 kΩ is a four-band part while 4.75 kΩ needs five. Enter the value you want and this gives the bands in reading order, starting from the end opposite the tolerance.

How it is calculated

digits = resistance ÷ multiplier · multiplier = the decade that leaves a whole number

The multiplier is chosen so the digits land in range: 10 to 99 for a four-band code, 100 to 999 for the longer ones. Values below ten ohms borrow the fractional multipliers, gold for a tenth and silver for a hundredth, which is why small resistors so often carry a gold third band.

Source: Vishay — Color Code and Standard Resistance Series, document 20143 (rev. 28-Aug-09): digit and multiplier columns

Questions people ask

Why does it refuse some values?

Because the bands cannot spell them. A four-band code carries two digits, so 4.7 kΩ works and 4.75 kΩ does not. Ask for five bands and it appears. If a value is refused at every band count, it is not a resistance anyone manufactures — the standard series exist so that two or three digits are always enough.

Which end do I paint first?

The bands come out in reading order: digits first, then the multiplier, then the tolerance, and the temperature coefficient last if you asked for six. On the part itself the tolerance band sits slightly apart from the rest, which is what tells a reader which end to start from.

What tolerance should I pick?

Gold, ± 5 %, is the everyday choice and the one you will find in any assortment box. Brown, ± 1 %, is the precision default and almost always appears on five-band parts. The tighter grades — green, blue, violet and grey — belong to measurement work rather than general wiring.

Can I paint a resistor that does not exist?

You can write the bands for any value the digits allow, but that is not the same as being able to buy it. Manufacturers make the standard series, so a value such as 3.7 kΩ has a perfectly good four-band code and no part behind it. Round to a series value before ordering.

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